1. Field of the Invention
The present invention relates to a semiconductor light emitting device including a current confinement layer formed by oxidation, particularly to a semiconductor light emitting device suitable for a red laser with a wavelength of around 600 nm to 700 nm.
2. Description of the Related Art
A laser diode whose parent material is AlGaInP provides red light emitting with a wavelength of 600 nm to 700 nm. Such a laser diode is widely used as a light source for performing high density recording by a DVD (Digital Versatile Disc) and the like.
FIG. 1 shows a cross section configuration of such a traditional red laser diode using AlGaInP. In the laser diode, for example, on a substrate 110 made of n-type GaAs, an n-type cladding layer 122 made of an n-type AlGaInP mixed crystal, an active layer 130 having MQW (Multiple Quantum Well) structure, a p-type cladding layer 141 made of a p-type AlGaInP mixed crystal, and a p-side contact layer 142 made of p-type GaAs are sequentially laminated. On the p-side contact layer 142, a p-side electrode 161 is provided. On the rear side of the substrate 110, an n-side electrode 162 is provided. Further, part of the p-type cladding layer 141 and part of the p-side contact layer 142 are removed by etching or the like, and a stripe-shaped ridge (projecting part) 180 for current confinement is formed. On the both sides of the ridge 180, a current blocking layer 181 made of n-type GaAs or the like is formed by epitaxial growth or the like, so that a current from the p-side electrode 161 can be concentrated on the ridge 180. In this structure, however, there is a disadvantage that a contact area between the p-side electrode 161 and the p-side contact layer 142 is decreased, and a contact resistance is increased.
In order to solve such a disadvantage, for example, as shown in FIG. 2, there has been a method, in which the ridge 180 is formed in the p-type cladding layer 141, the current blocking layer 181 is buried on the both sides of the ridge 180, and then the p-side contact layer 142 is grown on the whole area of the p-type cladding layer 141 and the current blocking layer 181. However, this method has a shortcoming that the number of crystal growth is increased, leading to increase in the manufacturing cost.
As a method to perform current confinement more simply, there is a method to form a current confinement layer by oxidizing part of an AlAs layer or an AlGaAs mixed crystal layer by moisture vapor. A laser diode having such a current confinement layer by oxidation has, for example, as shown in FIG. 3, a current confinement layer 151 having a conductive region 151A made of AlAs or an AlGaAs mixed crystal and a nonconductive region 151B made of aluminum oxide between a first p-type cladding layer 141A and a second p-type cladding layer 141B (For example, as an example of a VCSEL, refer to Japanese Unexamined Patent Application Publication No. 2003-69150). The side face of the first p-type cladding layer 141A, the current confinement layer 151, and the second p-type cladding layer 141B is covered with an insulating film 111. The p-side contact layer 142 and the p-side electrode 161 are contacted through an aperture of the insulating film 111.